Yes, a study, guest bedroom

Vote three of a library/guest room. I think it would look great with book cases in it. Love the ceiling BTW.

We had a similar dilemma when we purchased this house. The room is an odd shape and had a pony wall. It had load bearing posts, so we couldn't remove those. We made it into a Pub/Entertainment Center. Everyone who comes here says "What a cool room!" Great place to hang out with friends! Here is a link to how it evolved:From Dining Room to Pub

So many people do not need or use a formal dining room, so yours is a common dilemma.

With such a great ceiling & having the pillars I think the best choice would be a library/game room. Also If you can fit a daybed in with a trundle under it, I do not think most family guests would object to sleeping there.

Perhaps adding bookcases for a library including the daybed/trundle could be best.

I like the game room idea. A fun round table under the chandelier for games, puzzles, etc. If it's in your wheelhouse, you could put a hidden tv for video games. For adult time, this could be your library/den/after dinner drinks and dessert room. This room always makes me smile. A great library, eclectic dining and a place to play games and hang out. You could even remove the glass from the dining hutch and put a flat screen tv there. You could put a portable fridge in the bottom shelf, and a make a coffee bar (or wine bar) or jars of fun snacks and candies on the hutch for game night. If the hutch isn't valuable, you could fun it up with a color you love.

A Modern Gem · More Info

I turned mine into a music room, complete with piano, violin, viola and cello. It has the best acoustics in the house and the over-sized chandelier is great for being able to read sheet music.